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Hsp90 Recognizes a Conserved Motif in the A Chains of ADP‐Ribosylating Toxins that Move from the Endoplasmic Reticulum to the Cytosol
Author(s) -
Kellner Alisha,
Teter Kenneth
Publication year - 2019
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2019.33.1_supplement.780.4
Subject(s) - endoplasmic reticulum , cytosol , chaperone (clinical) , hsp90 , cholera toxin , biochemistry , chemistry , microbiology and biotechnology , biology , heat shock protein , enzyme , medicine , pathology , gene
Cholera toxin (CT) enters the cell via receptor‐mediated endocytosis and travels in a retrograde fashion to the endoplasmic reticulum (ER). The catalytic A1 subunit is then displaced from the rest of the holotoxin, unfolds, and is exported to the cytosol where it regains an active conformation for the ADP‐ribosylation of its G‐protein target. We have shown that the cytosolic chaperone Hsp90 is required for CTA1 translocation to the cytosol. We have also shown that Hsp90 is able to independently bind and refold CTA1. Using libraries of CTA1‐derived peptides, we have identified two distinct Hsp90 binding sites within the 192 amino acid protein, an N‐terminal RPPDEI (CTA1 11–16 ) motif and a C‐terminal LDIAPA (CTA1 153–158 ) motif. Peptides corresponding to either site were able to block Hsp90 from binding to full‐length CTA1, and both binding sites were required for translocation of CTA1 to the cytosol. The LDIAPA motif is unique to CTA1, but an RPPDEI‐like motif is present in four other ER‐translocating ADP‐ribosylating toxins: pertussis toxin, Pseudomonas aeruginosa exotoxin A, Escherichia coli heat‐labile toxin, and Salmonella Typhimurium ADP‐ribosylating toxin. Using site‐directed mutagenesis to further investigate the RPPDEI motif, we found that a modification of either proline residue blocks CTA1 translocation to the cytosol. Our work has identified, for the first time, specific amino acid sequences that are recognized by Hsp90 and are essential for toxin translocation from the ER to the cytosol. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .